1. Field of the Invention
The present invention relates, in a record reproducing apparatus for video, cassette, recorder or the like, to a method of allocating the recording signals (for example, audio signals and video signals) into a plurality of data tracks composed of a plurality of editing unit data so as to record them.
2. Description of the Prior Art
Conventionally, in a record reproducing apparatus, a recording method generally allocates the recording signals into a plurality of data tracks so as to effect the recording operation on a recording medium; the recording signals (for example, audio signals and video signals) are composed of a plurality of editing unit data. (For example, Richard brush; Design Consideration for the D - 2 NTSC Composite DVTR : SMPTE Journal: 182-193, March, 1988).
Here the data in one editing unit of the recording signal is defined to be the data in the least unit capable of rewriting in the recording of the new signals on the prerecorded part on the recording medium by a certain record reproducing apparatus. For example, assume that the recording signals are video signals, and the data in the editing unit become the data of the video signals of one field or one frame. Conventionally, a recording method is provided for allocating the data of a certain one editing unit as is on one data track on the recording medium without dividing the data in a certain one edition unit into a plurality of units so as to effect the recording operation.
The conventional recording method will be described hereinafter.
FIG. 10 is a format chart on the recording medium in the conventional recording method. Here, a recording method of allocating four editing units of data (the audio signals of four channels) into two data tracks is simply described, with the format of the other portions not being mentioned.
As shown in FIG. 10, the data (audio signals of four channels) "A1", "B1", "C1", "D1" of four editing units are allocated to the portions of 101, 102, 103, 104 of two data tracks. Namely, the data (the audio signal of one channel) of one editing unit is allocated to one data track without being divided.
The data of the editing unit in the other data tracks which are not shown in FIG. 10 are allocated onto the recording medium and recorded by a similar method.
But in the record reproducing apparatus adopting a recording method of allocating the recording signals composed of a plurality of editing unit data into a plurality of data tracks so as to record them, it is necessary to effect the tracing operation again with the head so as to renew (write one over another) only the portion on the recording medium to which the recording signal of a particular editing unit data is allocated when only a particular editing unit data is edited from a plurality of editing unit data of the recording signals.
But in the conventional recording method, as the data of one editing unit is allocated as is to one data track without being divided, the linearity of the track may often be shifted due to the mechanical accuracy problem, and is shifted especially during interchangeable reproduction (that is, the apparatus which has recorded the signals is different from the apparatus used to reproduce such signals). As a result, in the editing point, the interference of the overlapped writing and the erasure remanants occur on both sides of one track, with a problem that the reproducing signals are considerably deteriorated.
The reason will be described in detail hereinafter.
FIGS. 11A-11C are model chart showing how the reproduction signals are deteriorated at the editing point when the linearity of the track has been shifted. FIG. 11 A shows a record pattern chart with the audio signals of four channels being recorded in the time series in accordance with the format shown in FIG. 10. FIG. 11B is a record pattern chart in a case where the linearity of the track has been shifted by X1 in the track pitch direction in comparison with the record pattern shown in FIG. 11A, with the insertion edition to the editing point (editing unit data "A2") about the editing unit data "A1" through "A4" of the audio signal of one channel of the audio signals of four channels shown in FIG. 11A. FIG. 11C is a record pattern chart with the linearity of the track being shifted by X2 in an inverse direction to the record pattern shown in FIG. 11B as compared with the record pattern of FIG. 11A, with the connecting record being performed from the editing unit data "A3" about the record pattern recorded as in FIG. 11B.
In FIG. 11 C, when the shift (X1) of the track shown in FIG. 11B in the audio signal of one channel is opposite in direction in the shift (X2) direction of the track shown in FIG. 11C the majority of the editing unit data "C3" disappears due to the overlapped writing of the editing unit data "A2", "A3", thus deteriorating the reproduction signal of the editing unit data "C3" in the data track where the editing unit data "C3" has been allocated as shown in (1) portion. Likewise, even in the track where the editing unit data "A3" is allocated, the data "A3" of the prerecorded portion remains partially as the unerased remains, so that the reproduced signals of the newly recorded data "A3" (the portion of hatching) are deteriorated.